1. Field of the Invention
The present invention relates generally to devices for starting an internal combustion engine and, more particularly, but not by way of limitation, to apparatus for starting the engine of an automotive vehicle equipped with a device for utilizing the electrical system of the vehicle as a source of electrical power for operating power tools and the like.
2. Brief Description of the Prior Art
The alternator of an automotive vehicle is capable of generating power at a voltage sufficient for the operation of power tools and the like designed to operate from power supplied by public utilities at a higher voltage than is normally found in an automotive vehicle electrical system. Advantage has been taken of this capability to make electric power, suitable for operation of such tools, available at job sites which are not serviced by public utilities. For example, U.S. Pat. No. 3,845,321, issued Oct. 29, 1974 to Santilli, discloses a device which can be engrafted on the electrical system of an automotive vehicle to permit power tools to be operated at any location accessible to the automotive vehicle. Similarly, Laffoon, et al., have disclosed an electrical power generating system which mates an automotive type alternator with a small gasoline engine in U.S. Pat. No. 4,074,145, issued Feb. 14, 1978. The electrical circuit of the power generating system disclosed by Laffoon can also be engrafted on an automotive vehicle electrical system so that the engine and alternator thereof provide electrical power for operating power tools in the manner of the Santilli device.
The purposes served by an alternator in carrying out its normal functions in an automotive vehicle electrical system differ from the purpose of operating a power tool at a voltage comparable to that supplied by public utilities and this difference is reflected in the design of devices which utilize alternators to operate power tools. In the system disclosed by Laffoon, the alternator is caused to operate either in a relatively low voltage mode suitable for charging a battery in the electrical system of a gasoline engine or in a relatively high voltage mode suitable for operating a power tool. In the low voltage mode, the field winding of the alternator is energized via a voltage regulator so that the voltage of the output terminal of the alternator is controlled to a value suitable for charging the battery and such output terminal is electrically connected to the battery for this purpose. In the high voltage mode, the output terminal of the alternator is electrically disconnected from the battery, for example, by grounding the gate of an SCR interposed between the alternator and the battery in order to prevent damage to the battery by the relatively high voltage output of the alternator. Means are also provided for energizing the field winding via the battery rather than via the voltage regulator and for increasing the speed of the engine driving the alternator so that the output voltage can be increased from the value normally utilized to maintain a charge on the battery. A solenoid connected to the throttle of the engine is utilized for increasing the engine speed. Where the engine and alternator are part of an automotive vehicle, the means for increasing the engine speed can utilize the vehicle engine vacuum source as disclosed by Santilli.
It will be clear that in many situations a power tool is utilized only intermittently and both Laffoon, et al., and Santilli disclose circuitry for automatically switching the alternator between the two modes of operation. Specifically, when a power tool is connected to either of the systems disclosed by Laffoon, et al., or Santilli and switched on, a current is passed through the tool, regardless of the mode of operation of the alternator, and this current is sensed by circuitry which causes the alternator to go to the high voltage mode, if it is not already in such mode, and remain in such mode during such time that the power tool remains in the switched on condition. Thus, at such times that the power tool is used, the alternator is in the high voltage mode to supply power for the tool. When use of the tool is discontinued, the switching circuitry causes the alternator to drop back to the low voltage mode, the engine speed to drop back to idle, and the alternator to be electrically connected to the battery for charging the battery.
While the art thus discloses devices which are suitable for providing electrical power for operation of tools at remote job sites, one problem has heretofore remained unsolved. In many applications, the device supplying electrical power will be located some distance from the location at which the power is to be used. Moreover, the use of a power tool will, in general, be phased into whatever task is being carried out so that the need for power may arise some time after the task is begun and it may arise only at infrequent intervals. Thus, in devices presently available, the gasoline engine, whether it be that of an automobile as disclosed by Santilli or a separate engine as disclosed by Laffoon, et al., must either be operated at times during which electrical power is not needed or a person carrying out a task requiring occasional use of a power tool must interrupt his work to start the gasoline engine which forms the primary power source for operating power tools.